Process for preparing a jet fuel



March 30, 1965 P. G. BERCIK ETAL PROCESS FOR PREPARING A JET FUEL FiledMarch 20. 1962 SMS Qh.

mthan the aromatic content of the cycle oil.

ho-nditions, extracts composed of 90 to 97 percent aro- United StatesPatent Otitice 3,175,970 PRGCESS FOR PREPARING A JET FUEL Paul G.Bereik, Glensllaw, Harold Beuther, Gibsonia, and Alfred M. Henke,Springdale, Pa., assignors to Gulf Research & Development Company,Pittsburgh, Pa., a corporation of Delaware Filed Mar. 20, 1962, Ser. No.180,963

3 Claims. (Cl. 208-212) This invention relates to a process for makingfuels for jet engines and more specifically jet fuels which have beentermed JP-X Fuels.

The JP-X Fuels must have the following properties: A net heat ofcombustion of over 18,350 B.t.u.s per pound of the fuel and over 135,000B.t.u.s per gallon of the fuel. Further, fuels of this class must havegood low temperature lluidity properties, below 40 F. freeze point andexcellent thermal stability. It is apparent `that the prioduction offuels meeting these specifications presents a difficult problem,particularly when it is recognized that the fuels must be made at areasonable cost.

We have discovered in accordance with the invention that fuels meetingthese specications can be prepared efliciently by the process describedmore fully hereinafter. The charge stock for the process is acatalyticcycle gas oil formed when heavier oils are cracked in conventionalcatalytic cracking units. In the present process the cycle gasoil isfractionated to obtain a fraction having an initial boiling point of atleast about 475 F., a 50 percent point above about 550 F., a 75 percentpoint above about 675 F. and anend point lower than about 715 F. Cyclegas oils of this type contain a high percentage of aromatichydrocarbons. We have found that an excellent jet fuel can Abe obtainedusing a cycle gas oil of the boiling ranges referred to `above andemploying a process involving additionally a solvent extraction of thecycle gas oil and subjecting the extract to a hydrogenation pretreatmentto reduce substantially the sulfur and nitrogen content of the extract.The extract, after removal of sulfur and nitrogen, is subjected to asaturative hydrogenation treatment to convert the aromatic hydrocarbonsto saturated condensed ring hydrocarbons.

The invention will be understood more clearly by reference to theaccompanying drawing which is a flow diagram illustrating a preferredmanner of carrying out the process of the invention. Referring to thedrawing, a fractionof cycle oil as described above is flowed throughline 1 to a solvent extraction column 2. Solvent is introduced into the.column through line 3. The rathnate is withdrawn from the bottom ofcolumn 2 through line d and may be `processed for recovery of solvent.The extraction is carried out so `as to obtain an extract yield equal toor less than the aromatic content of the cycle oil and for best results`the extraction is carried out so as to obtain an extract yeld of about5 to about 20 percent by volume'less Under these matics c an=beobtained.

The solvent extract stream is withdrawn through lineS and `fed to adistillation column 6 where the solvent is evaporated and withdrawnthrough line 7. The extract is Withdrawn as bottoms from distillationcolumn y6 through line 8. The extract is .then mixed with hydrogenintroduced through `line 9 and the mixture is Vflowed through line 10 toheater 1l. The resulting mixture is flowed through line 12 to a tirstcatalytic hydrogenation unit 13, wherein the extract is subjected to arelatively mild catalytic hydrogenation effective however to reduce the`nitrogen and sulfur content `ot the extract to a low level. `We `havefound that if the sulfur and/or nitrogen content of the treated extractis too high, the catalyst employed for the saturative hydrogenation willbe rapidly deactivated and the fuel produced Will have poor stability,owing to relatively high aromatic, sulfur and nitrogen contents. Inaccordance with the invention the first hydrogenation is preferablycarried out so as to reduce the sulfur in the extract to less than 150ppm. and the nitrogen content to less than 30 ppm. The treated product,together with excess hydrogen, is removed from the bottom of catalytichydrogenation unit 13 through line 14 to a conventional separator 15 inwhich excess gas is separated frorn the hydrogenated extract. Excess gasis removed through line 16 to a gas scrubber, not shown. After theseparation, the treated extract is flowed through line i7 in admixturewith hydrogen introduced through line 18 and the mixture is introducedthrough line 19 into a heater 20. The heated product is then ilowedthrough line 21 into a second catalytic hydrogenation unit 22. Thishydrogenation unit is operated so as to saturate the aromatichydrocarbons in the extract. The hydrogenated extract is Withdrawn fromthe hydrogenation unit through line 23 to a separator 2d from whichexcess hydrogen is removed through line 25 and may beused as recycle tothe hydrogenation units. The substantially `completely hydrogenatedproduct is yremoved from -the separator through line 26 to afractionator 27 and the JP-X Fuel is removed from the fractionatorthrough line 28 and thence to storage. Lighter and heavier fractions arewithdrawn through lines 29 and 30, respectively.

ln order to describe the invention more clearly, it is pointed out thatthere are five rnain elements making .up the process. The first is theselection of the charge stock. While any cycle oils having the.properties within the ranges heretofore described are satisfactorycharge stocks for the process, we prefer in accordance with theinvention to employ cycle oils or fractions of such oils having initialboiling points higher than about 500 F.,l a 50 percent point higher thanabout 600 F., a 75 percent point less than about 650 F. and an end pointless than about 690 F. Use of cycle stocks having these inspectionsresults in jet fuels having good volumetric heats of combustion and lowfreezing points, and, in addition, the yields of the fuels areexcellent.

The invention will be understood more fully by reference to thefollowing example.

Example The catalytic cycle oil treated in this example had`approximately the following composition, percent by weight:

S15-600 F. 50.0 60G-650 F. 37.5 G50-685 F. 12.5

This cycle oil was subjected to solvent extraction with acetonitrile asthe solvent. The volume ratio of the solvent and cycle oil was 1:1 andthe extraction Was carried out ata temperature of F. The extract wasthen sub.- jected to catalytic hydrogenation which reduced substantiallythe nitrogen and `sulfur in the extract. The catalyst employed in thisrhydrogenation was a nickel tungsten catalyston an alumina non-crackingbase. 32 percent of the catalyst was composed of `equal partis of nickeland tungsten, the rest being the alumina base.. The hydrogenation wascarried out at a temperature of about 723 F., a pressure of about 1000pounds per square inch gauge, and a. hydrogen circulation rate of 4000s.c.f./ bbl. The liquid space velocity, volume per volume per hour, was0.5.

VThe treated extract substantially free of nitrogen and sulfur was thensubjected to a less severe hydrogenation which was effective to saturatethe aromatic hydrocarbons. The catalyst .employed in this phase of theprocess was a catalyst comprising nickel deposited on keiselguhr inwhich 48 percent by `weightof the catalyst was Patented Mar. 30, 1955nickel. This hydrogenation was carried out at a temperature of 5715 F.,a pressure of 1000 p.s.i.g. and a hydrogen circulation rate (standardcubic feet per barrel) of 8000. The liquid space velocity, volume pervolume For the first hydrogenation of the extract any of the familiarhydrogenation catalysts can be used, provided the catalyst does not havestrong catalytic cracking properties at the hydrogenation conditionsemployed. For

per hour, was 0.5. The product yield, percent by volume 5 example,catalysts comprising one or more metals such of the cycle oil, was asfollows: as cobalt, nickel, molybdenum, or tungsten deposited on .anon-cracking base can be used. Further, it will heV xgact 5'02understood that the temperatures for this operation can SJCQ g-lure-I bevaried, depending upon the charge stock. For exam- 350425, F' t fuel10'0 10 ple, temperatures w1th1n the range of about 600 to 800 600., F'Je F. can be used. Also, the pressure employed in this .-I- fuel 2.2180 350 F. gasoline 2.6 operation can be var-ied'withrn the range of 500to 5000 p.s.1.g. and space velocities within the range of 0.2 to 3.0 In4the following table the product inspections are set can be used,depending upon the other variables. Fur-l out. ther, the hydrogencirculation rate can be varied over the Cycle First Final 425-600"35o-254 Product Inspections, Description Oil Eytract Hydro- Hydro- F.,F., Jet

genation genation .TP-X Fuel Aromatics, percent by Vol 55. 0 92. 3 62.5 1. 5 2. 8 1. 9 Heat o Combustion, Net:

Btn/1b. 18,404 18,542 aan/gal-. 135,269 131,371 Freeze Point; F. -7Sulfur, percent 1. 28 2.12 .003 Nitrogen, percent 0.035 0.055 .008

A fuel prepared in accordance with the example Was range 2500 to 10,000standard cubic feet of hydrogen per tested to determine its thermalstability. The test em- 30 barrel. ployed was the CFR Fuel Coker TestProcedure. This As stated heretofore, the second hydrogenation is detestprocedure is described in detail in the Manual of signed to convert thearomatic extract to a product corn- ASTM Standards on PetroleumProducts, ASTM D posed substantially of saturated condensed ring hydro-1660-59T. In accordance with this test method, aviation carbons. Whilethe catalyst employed in the specific turbine fuels are subjected toflow conditions and temexample is a highly efficient catalyst for thispurpose, perature stresses similar to those in combustion gas turitshould be recognized that other hydrogenation catabine or jet aircraftengines by circulation through a simulysts can be employed to achievegood results. Some lated aircraft fuel system at a temperature above 300examples of such catalysts are 0.5 to 5 percent palladium F., at a rateof 6 pounds of fuel per hour, for a period or platinum supported onalumina and 15 percent to 50 of 300 minutes. The test apparatuscomprises a fuel syspercent nickel supported on alumina. tem containingtwo heated sections, one of which is a Further, the process conditionsfor the second hydropreheater section that simulates the hot fuel linesections genation can be varied. For example, depending upon of anaviation turbine engine as typified by the engine the other variables,-the temperature may be between fuel lubricating oil cooler. The extentof fouling of heat about 400 to 700 F., the pressure may range fromabout transfer surfaces in the preheater section by fuel degrada- 500 toabout 5000 p.s.i.g., and the hydrogen circulation tion deposits isdetermined by inspection and the extent rate may vary between about 2500to 10,000 standard of such foul-ing is used as one index of thetemperature, cubic feet of hydrogen per barrel. The space velocitystability of the aviation turbine engine. Preheater deemployed may, forexample, be in the range of about 0.2 posits are rated according to thefollowing scale: 0=no to 3. visible deposits; 1=visible haze or dulling,but no visible 50 Obviously many modifications and Variations 0f thecolor; 2=barely visible coloration; 3=light tan to peainvention ashereinbefore set forth may be made without cock stain; 4=heavier than 3.departing from the spirit and scope thereof, and therefore 'Ihe secondheated section comprises a filter section only such limitations shouldbe imposed as are indicated that simulates the nozzle area or fuel inletarea of the in the appended claims. combustion zone of a jet enginewhere fuel degradation We claim: particles may be trapped. A precision,sintered stainless 1. A process of making a hydrocarbon compositionsteel filter is employed in the lilter to trap fuel degrada; Iadapted tobe employed as a jet fuel which comprises tion particles formed duringthe test. The extent of the fractionating a catalytic cracking cycle oilto obtain a build-UP 0f fuel degradation particles in the lter sectionfraction containing nitrogen and sulfur and having an is indicated bythe pressure dilferential across the filter initial boiling point morethan 475 F., a 50 percent and this pressure differential is used asanother index of point more than 550 F., a 75 percent point less thanthe hightemperature stability of the aviation turbine fuel. 675 F. andan end point less than 715 F., solvent ex- In carrymg out the testdescribed, the temperature of the tracting said fraction, recovering theextract, reducing fuel at the outlet of the preheater section wasmaintained the sulfur and nitrogen content of said extract by catalyticat 450 F. and the filter temperature wals maintained at 65hydrogen-ation, catalytically hydrogenating the resulting 500 F-composition to saturate said composition, fractionating The results ofthis test were the following: The flter the resulting hydrogenatedcomposition, -and recovering pressure drop in inches of mercury was 0.1and the prefrom said hydrogenated composition a fuel having a net heaterdePosits were zero. heat of combustion of more than 18,350 B.t.-u.s perIt will be understood that changes' can be made in the 70 pound and morethan 135,000 B.t.u.s per gallon of the process described in the exampleWithout departing from fuel. the scope of the invention. In the solventextraction step 2. A process of making a hydrocarbon composition of theprocess, other solvents can be employed in place adapted to be employedas a jet fuel which comprises of acetonitrile; for example, furfural,sulfur dioxide, amfractionating a catalytic cracking cycle oil to obtaina monia and ethylene glycol can be employed` fraction having an initialboiling point of at least about 500 F., a 50 percent point more thanabout 600 F., a 75 percent point less than 650 F. and an end point lessthan 690 F., solvent extracting said fraction, recovering the extract,reducing the sulfur and nitrogen content of said extract by catalytichydrogenation, catalytically hydrogenating the resulting composition tosaturate said composition, fractionating the resulting hydrogenatedcomposition, Aand recovering from said hydrogenated con1- position afuel having a net heat of combustion of more than 18,350 B.t.u.s perpound and more than 135,000 B.t.u.s per gallon of the fuel.

3. A process of making a hydrocarbon composition adapted to be employedas a jet fuel which comprises fractionating `a cycle oil from catalyticcracking to obtain a fraction containing nitrogen and sulfur and havingan initial boiling point more than 475 F., a 50 percent boiling pointmore than 550 F., ya 75 percent boiling point less than 675 F. and anend point less than 715 F., solvent extracting said fraction, recoveringthe extract, reducing the sulfur and nitrogen content of said extract bycatalytic hydrogenation, catalytically hydrogenating the resultingcomposition to saturate said composition, fractiona-tng .the resultinghydrogenated composition, and recovering 'from said hydrogenatedcomposition a fuel adapted for use Ias a jet fuel.

References Cited by the Examiner UNITED STATES PATENTS 3,001,932. 9/61Pietsch 208-216 3,077,733 2/63 AXe et al. 208--143 ALPHONSO D. SULLIVAN,Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,175,970 March 30, 1965 Paul G. Bereik et a1.

rs in the above numbered pat- It is hereby certified that error appeaetters Patenil should read as ent requiring correction and that the saidL corrected below.

Column 1, line 55, for "yel 3 and 4, in the table, heading to for"S50-Z540" read S50-4259 d" read yield columns the seventh columnthereof,

Signed and sealed this 17th dayolf-August 1965.

(SEAL) Attest:

EDWARD J. BRENNER ERNEST W. SWIDER Avttesting Officer Commissioner ofPatents

1. A PROCESS OF MAKING A HYDROCARBON COMPOSITION ADAPTED TO BE EMPLOYEDAS A JET FUEL WHICH COMPRISES FRACTIONATING A CATALYTIC CRACKING CYCLEOIL TO OBTAIN A FRACTION CONTAINING NITROGEN AND SULFUR AND HAVING ANINITIAL BOILING POINT MORE THAN 475*F., A 50 PERCENT POINT MORE THAN550*F., A 75 PERCENT POINT LESS THAN 675*F. AND AN END POINT LESS THAN715*F., SOLVENT EXTRACTING SAID FRACTION, RECOVERING THE EXTRACT,REDUCING THE SULFUR AND NITROGEN CONTENT OF SAID EXTRACT BY CATALYTICHYDROGENATION, CATALYTICALLY HYDROGENATING THE RESULTING COMPOSITION TOSATURATE SAID COMPOSITION, FRACTIONATING THE RESULTING HYDROGENATEDCOMPOSITION, AND RECOVERING FROM SAID HYDROGENAT*ED COMPOSITION A FUELHAVING A NET HEAT OF COMBUSTION OF MORE THAN 18350 B.T.U''S PER POUNDAND MORE THAN 135000 B.T.U.''S PER GALLON OF THE FUEL.